This invention is concerned with chloroisocyanurates selected from the group consisting of trichloroisocyanuric acid, dichloroisocyanuric acid, and the alkali metal salts of dichloroisocyanuric acid. Such isocyanurates are manufactured in substantial quantities for various uses, e.g. as sanitizing and bleaching agents which release available chlorine in aqueous media.
Normally, such isocyanurates are manufactured, shipped and/or stored under conditions that include the presence of small amounts of water (e.g. water vapor in the air) and this water, which may become partly entrained in and/or adsorbed on particles of the isocyanurate, tends to react slowly with the isocyanurate liberating, over an extended time, various hydrolysis and decomposition products including, e.g. HCl, Cl.sub.2, HOCl, NH.sub.2 Cl, Cl.sub.2 O, NHCl.sub.2 and NCl.sub.3. Even in the absence of water, heat may cause some decomposition of these compounds.
Because of their strong oxidizing potential, such isocyanurates are generally shipped and stored in closed (gas-tight) containers, e.g. drums. Hydrolysis and decomposition of the isocyanurates in such containers are highly temperature dependent and under warm weather conditions, the concentration of chlorine-containing hydrolysis and/or decomposition products in the vapor space within such containers can rise to undesirable levels. Accordingly, the desirability of techniques for lowering that concentration has been recognized.
For example, U.S. Pat. No. 3,061,549 issued Oct. 30, 1962 to M. L. Dickey disclosed that decomposition products of di- and trichloroisocyanuric acid can be converted to compounds having no objectionable odor by reaction with various "deodorant" materials. However, as shown hereinafter, the potential for reaction of such materials with the chloroisocyanuric acids can present a substantial danger of fire or explosion. Moreover, merely converting the decomposition products to non-odorous compounds may not render them safe.
In another approach to the problem, U.S. Pat. No. 4,149,988 issued Apr. 17, 1979 to J. P. Brennan recognizes the desirability of inhibiting decomposition of the chloroisocyanurates using compounds which are unreactive therewith and insensitive to moisture, and discloses that such a result can be obtained using alkaline earth metal sulfates. However, as also shown hereinafter, such sulfates are not effective with mixtures containing higher concentrations of chlorine-containing compounds.
In the absence of an adequate solution to this problem, it is an object of this invention to provide a technique useful in lowering the concentration of chlorine-containing compounds in a gaseous mixture in contact with such a chloroisocyanurate and, additionally, to prevent the accumulation of such compounds therein. In view of the great reactivity of the chloroisocyanurates, it is desirable that such a technique can be carried out using materials which are essentially unreactive with the chloroisocyanurates and with products of their decomposition and/or hydrolysis.
Another object of the invention is to use a material which will achieve and maintain those results over extended periods of time, and under adverse conditions including elevated temperatures. Another object is to use a material which is stable against chemical attack by the chloroisocyanurates and their decomposition and hydrolysis products, and by water so that such a material does not lose its effectiveness due to such attack. A further object is to use a material that is innocuous to personnel and equipment, easy to handle and of reasonable cost.